Optical distribution shelf for a remote terminal of an optical fiber telecommunications network

ABSTRACT

In an optical fiber telecommunications network for providing both narrowband telephony signals and broadband video services over a single optical fiber using a single optical carrier, an optical distribution shelf includes a plurality of optical distribution units and interface units for interfacing with a controlling microprocessor. The optical distribution units receive baseband TDM telephony signals in serial format and the broadband video signals and function to frequency division multiplex the broadband video signals with the baseband telephony signals. The multiplexed signal is used to frequency modulate an optical carrier for transmission on a single optical fiber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 07/738,315 filed on Jul. 31,1991, now U.S. Pat. No. 5,576,874.

This application describes an invention which is related to a pluralityof inventions covered by the following commonly assigned and in somecases co-pending U.S. patent applications: Ser. No. 351,861 filed May12, 1989; Ser. No. 452,291 filed Dec. 15, 1989; Ser. No. 295,887 filedJan. 11, 1989, now U.S. Pat. No. 5,014,268, issued May 7, 1991; Ser. No.351,458 filed May 12, 1989; Ser. No. 451,419 filed Dec. 15, 1989; Ser.No. 451,436 filed Dec. 15, 1989 now U.S. Pat. No. 4,993,019 issued Feb.12, 1991; Ser. No. 547,383 filed Jul. 3, 1990, now U.S. Pat. No.5,027,349 issued Jun. 25, 1991; Ser. No. 616,175 filed Nov. 20, 1990;and co-pending applications Ser. No. 07/738,111, entitled, "SwitchedVideo Architecture for an Optical Fiber-to-the-Curb TelecommunicationsSystem"; and Ser. No. 07/739,203, entitled "Fiber Optic Link", bothfiled on Jul. 30, 1991. The Disclosures of the above-mentionedapplications and patents are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical fiber telecommunicationsnetwork and more particularly, to such a network that provides bothnarrowband telecommunications signals and broadband switched videosignals. The invention provides an optical distribution shelf for use ina remote terminal for distributing optical signals to distributionfibers extending to remotely-located optical network units.

2. Description of the Prior Art

The rapid proliferation of optical fiber telecommunications systems hasmade possible the provision of broadband services to individualsubscribers on a relatively universal basis. Such broadband servicesoften include data transmission; however, there is a broader market forthe distribution of video signals over the telecommunications network.

The provision of such video services has long been desired; however, thepreviously proposed systems have all been subject to variousdeficiencies which have prevented their commercial acceptance. Videosignals may be broadcast to all subscribers over optical fibers;however, this severely limits the programming selection and the numberof channels that may be available to each subscriber. A switched videoarchitecture allows for the provision of significantly more programmingoptions and control of distribution only to authorized subscribers.

The concept of switched video transmission systems has been proposed inthe past; however, most proposals have had undesirable features. Mostproposed switched video architectures require the use of a secondoptical fiber to distribute the broadband services or, as analternative, the use of a wavelength division multiplexing system. Suchsystems do not offer a truly integrated architecture, wherein a singlefiber distributes both narrowband and broadband signals and the systemsare not integrated with respect to both control and cost effectiveutilization of common electronics.

The use of two fiber systems to distribute the broadband video serviceis inefficient in that the second fiber must be installed during theinitial deployment of the system when there are extremely high equipmentexpenses. Currently, regulatory agencies do not always permit recoveryof costs associated with a second fiber for broadband services. The useof wavelength division multiplexing significantly complicates a systemin that it requires the use of a significant number of fiber couplerswhich are both high cost and large components. Both alternativestypically double the amount of costly optoelectronics required.

In unidirectional (two-channel) wavelength division multiplexing twodistinctly different optical sources and detectors are utilizedsimultaneously. These sources and detectors must be coupled to thesingle transmission fiber. Separate transmitters and receivers mustaccompany each source and detector. This multiplicity of fibers andcouplers becomes extremely difficult to handle and requires large andcumbersome equipment or delicate optical arrangements. The need forseparate transmitters and receivers for each wavelength makes the costprohibitive, particularly when universal service is rendered to allcustomer premises.

An article entitled: "A Future Switched Video System" by John R. Gunter,IEEE LCS Magazine, February, 1990, at page 66 and following, describesthe desirability of providing video services over the telecommunicationsnetwork. Another article entitled: "A High-Quality Switched FM VideoSystem" by David E. Robinson and David Grubb, III, IEEE LCS Magazine,also published February, 1990, at page 53 and following describes aproposed system architecture wherein the various video channels arefrequency multiplexed onto a carrier; however, the carrier useswavelength division multiplexing for upstream and downstreamtransmissions.

Other articles describing the simultaneous transmission of narrowbandand broadband signals are as follows: "A Hybrid Lightwave TransmissionSystem for Subcarrier Multiplexed Video and Digital B-ISDN Services inthe Local Loop", by Charles N. Lo, Journal of Lightwave Technology, Vol.7, No. 11, November 1989, pp. 1839-1848; and "Fiber Optic Analog-DigitalHybrid Signal Transmission Employing Frequency Modulation", by K. Satoet al, IEEE Transactions on Communications, Vol. COM-33, No. 5, May1985, pp. 433-441.

The upstream and downstream transmission of control information hasconsistently been a problem in switched video and video on demandsystems. Such upstream transmission has been accomplished usingwavelength division multiplexing as previously mentioned in the articleof David E. Robinson et al; however, such a system is then subjected tothe aforementioned deficiencies associated with the use of wavelengthdivision multiplexing. Other systems have used a separate narrowbandtelephone connection for keying in control data in the upstreamdirection using a telephone subset. Such systems are not trulyintegrated and require the use of the premises telephone subset totransmit control information upstream for selection of the desiredvideo. The RCV-1G system provided by Alcatel used a dedicated FSKsubcarrier electrically multiplexed with the narrowband and video forcontrol purposes.

Thus, the prior art has not provided a commercially acceptablearchitecture for mass deployment of switched video on atelecommunications network.

SUMMARY OF THE INVENTION

The present invention contemplates a truly integrated fiber optictelecommunications network providing switched video and standardnarrowband telephone services. The system is integrated in that ittransmits video services on the same fiber as the narrowband servicesand uses common equipment to support both services. Significantadvantages of the present invention are realized through the use of anarchitecture which implements frequency division multiplexing of thenarrowband telephone service and control signals with FM channels forvideo distribution. These frequency division multiplexed signals aresummed electrically and are modulated onto an optical carrier having awavelength of approximately 1310 nm. Of course, the system can be usedwith other wavelengths if practical sources are available. The use ofthis type of system architecture allows for the choice of a much largernumber of video channels, for example 192 channels, than the previouslyoffered services while keeping equipment cost to a minimum.

The present architecture utilizes a frequency modulated carrier insteadof the prior art AM-VSB modulated carriers. An intermediate frequency ofabout 850 MHz is used which is higher than the 45.75 MHz used in priorart devices. Integration of broadband and narrowband signals on the sameoptical wavelength eliminates the need for the costly use of wavelengthdivision multiplexing in which the broadband and narrowband signals weretransmitted at different wavelengths.

The present invention utilizes a Loop CarrierCross-connect-Fiber-To-the-Curb (LCX-FTC) System, which is an advancedSONET compliant Digital Loop Carrier (DLC) system that offers telephonecompanies immediate and future access to narrowband and broadbandfunctionality. The system is designed around a family of SONET accessproducts produced and sold by Alcatel NA Network Systems Corp., theassignee of the present invention, under product designations LCX-50 andLCX-150. The LCX-FTC system utilizes optical fibers instead of metalliclines in the local loop. The Fiber-To-The-Curb (FTC) components of theLCX-FTC system are built upon the Loop Carrier Cross-connect (LCX)hardware and software platforms of Alcatel to provide an easy migrationto the FTC services. The LCX-FTC system is modular by design and can beconfigured to accommodate many different applications.

The above-mentioned patents and patent applications which have beencross-referenced as related inventions fully describe the members of theLCX family of access products upon which the present invention is based.Accordingly, the teachings included in these patents and patentapplications are incorporated herein by reference.

In the present invention a SONET OC-1 (51.84 Mb/s) or OC-3(155.52 Mb/s)feeder provides the digital transport link from the Central Office (CO)equipment to the Remote Terminal (RT) sites. The system is adaptable foruse with Universal Digital Loop Carrier arrangements or for IntegratedDigital Loop Carrier arrangements. The system uses a star distributionnetwork where the optical fibers radiate from the RT to active OpticalNetwork Units (ONU) via point to point optical links with eachresidential ONU serving up to eight living units with three DS0 (64Kb/s) channels. For residential applications two channels are typicallyused to provide Plain Old Telephone Service (POTS) with the thirdchannel reserved for future applications such as the D-channel forIntegrated Services Digital Network (ISDN). An ONU designed for businessapplications could provide more channel capacity and services per ONUthan the residential ONU.

A non-blocking switch fabric is built into the RT core module to allowsubscriber channels from the ONUs to be loaded and groomed over the RTto CO feeder for optimum capacity and ease of administration.

This basic architecture of an LCX-FTC system allows for easy andeconomical upgrades to system capabilities such as broadband videotransmission which is the subject of this invention. The broadbandcapability is available as an upgrade to the narrowband system to yieldthe integrated FTC system. Utilizing an efficient and economical methodfor adding switched video channel capability, the LCX-FTC systemprovides the capability of expanding channel capacity to the ONUs asdemand increases, without large upfront expenditures in CO or RTbroadband equipment. Each residential ONU is capable of providing up to48 simultaneous video channels at the rate of six channels for each ofeight living units thus, future customer demands will be easily met.

The broadband service will provide for the transmission of up to 24switched video channels over the same optical link as the narrowbandchannels. Two upstream, ONU-To-RT, video channels per ONU are alsoavailable. The capacity for an additional 24 video channels per ONU canalso be added when needed to serve greater than four living units, byuse of a second optical fiber. It is contemplated that the second fiberwill be deployed along with the first fiber, but not used until needed.The broadband equipment is optional at the initial deployment of thenarrowband system and can be added when required. The upgrade permitsimmediate deployment of switched video services, which services includebasic programming, premium programming, Pay-Per-View (PPV),Impulse-Pay-Per-View (IPPV) and Video-On-Demand (VOD) from multipleservice providers. The technology used allows either analog or digitaltelevision signals to be delivered to the subscriber. The switched videotechnology allows the subscriber to select from a range of typically upto 192 different programming channels. Using a broadcasting technique,this many program channels could not be simultaneously provided to thesubscriber residents without prohibitive expense due to the requiredbandwidth.

The frequency spectrum reserved for the video channels from the RT tothe ONU over a fiber is from 60 to 780 MHz, which supports twenty-four,30 MHz wide, channels per ONU. At each ONU video service is availablefor up to four living units with six channels each reserved for eachliving unit. Thus, each of the four living units can subscribe to andreceive one to six simultaneously switched video channels. A set-topconverter, or television with built-in controller, sends programselection information upstream to the RT where video switching equipmentplaces the selected program on the subscriber's distribution channel. Asecond distribution fiber to the ONU is used when video service isrequired by any additional living units over and above four units.

The broadband equipment uniquely uses the LCX-FTC narrowband system forcontrol and communication. The upstream control information istransmitted over a video control channel using one DS0, in thenarrowband spectrum.

In addition to the commonality of electronics, there exists commonalityin the mechanical components which reduces the cost of the broadbandupgrade.

The present invention is particularly directed to the provision of anOptical Distribution Shelf (ODS) that replaces up to seven metallic lineshelves in a standard LCX-50 remote terminal. The ODS is connected tothe 28 A and B SBIs from the LCX-50 core. The ODS decides which of the Aand B SBIs is active and utilizes the narrowband telephone signalsreceived therefrom. The ODS includes a plurality of Optical DistributionUnits (ODU) connected to the SBIs and also connected to receive theswitched video signals. The ODUs frequency, division multiplex theswitched video signals onto the narrowband telephone signals andthereafter perform an electro-optical conversion to provide an opticaloutput containing both broadband switched video signals and narrowbandtelephony signals on one optical carrier over one optical fiber. The ODSfurther includes a Common Shelf Alarm Unit (CSAU) and a RemoteMeasurement Unit Interface (RMUI), which units function as an interfaceto the microprocessor contained within the LCX core.

A primary objective of the present invention is to provide an ODS foruse in a RT for providing a plurality of optical signal outputs todistribution fibers.

Another objective of the present invention is to provide ODUs responsiveto signals from SBIs for providing narrowband telephony signals todistribution fibers.

Another objective of the present invention is to provide ODUs whichfunction to frequency division multiplex broadband video channels withnarrowband telephony signals to provide integrated broadband andnarrowband signals which are modulated onto an optical carrier over asingle optical fiber.

Another objective of the present invention is to provide controlmechanisms for providing an interface with the microprocessor of an LCXcore for controlling the ODUs.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a basic narrowband FTC architecture whichcan be upgraded to provide broadband service.

FIG. 2 is a block diagram illustrating one embodiment of the overallsystem of the present invention.

FIG. 3 is a block diagram showing a remote terminal of an LCX-FTCequipped for narrowband service.

FIG. 4 is a block diagram of an optical distribution shelf as shown inFIG. 3.

FIG. 5 is a block diagram showing how an ONU fits into the overallsystem.

FIG. 6 is a block diagram of an ONU.

FIG. 7 is a block diagram showing how the LCX-FTC is utilized to providebroadband services.

FIG. 8 is a block diagram showing the basic broadband functions of aremote terminal.

FIG. 9 illustrates how FIGS 9A and 9B fit together.

FIGS. 9A and 9B are together a block diagram illustrating how theLCX-FTC system provides broadband services.

FIG. 10 shows a block diagram of a video line card as shown in FIG. 9.

FIG. 11 is a diagram showing how broadband services are delivered to aliving unit.

FIG. 12 is a block diagram of a switched video distribution card asshown in FIG. 9.

FIG. 13 is a block diagram showing the ONU broadband interfaces.

FIG. 14 is a block diagram of a broadband interface unit.

FIG. 15 shows how FIGS. 15A and 15B fit together.

FIGS. 15A and 15B are a block diagram illustrating the broadband videocontrol architecture.

FIG. 16 is a block diagram of a video control unit.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Referring to FIG. 1 there is shown a CO 10 connected to remote terminals12 via SONET OC-1 or OC-3 optical feeders 14 which function as a digitaltransport link therebetween. The carrier rate used for transport dependsupon the current and anticipated channel capacity required. The CO 10may include either an LCX-50 or LCX-150 Central Office Terminal (COT)for UDLC arrangements or a TM-50 or ADM-150 for IDLC arrangements. TheUDLC system is suited for COs with an analog switch using metallic lineshelves to provide the analog interface to the switch. The IDLC systemarrangement provides a DSX-1 interface with TM-50 or ADM-150 units forCOs using a digital switch. Both TR-8 and TR-303 digital interfaces aresupported by the LCX-FTC system. An LCX-50 core provides the platformfor OC-1 rate transmission and an LCX-150 core will provides a platformfor OC-3 rate transmission. The structures necessary for the TM-50 andADM-150 units are similar to those disclosed in the aforementioned U.S.patent application, Ser. No. 351,861 filed May 12, 1989 and thestructures for LCX-50 and LCX-150 cores are disclosed in U.S. patentapplication, Ser. No. 452,291, filed Dec. 15, 1989.

The telecommunications system uses a star distribution network where theoptical fibers radiate from the RTs 12 to active ONUs 16 via point topoint optical distribution links 18. Each LCX-50 equipped RT 12 canserve up to 24 or 28 ONUs, depending on whether broadband service isbeing offered. The RT serves the ONUs through optical links 18. When theRT is equipped with an LCX-150, 168 ONUs can be served with narrowbandand broadband services. Each ONU 16 can service up to eight living unitsor homes 20 and is connected thereto through the use of metallic twistedpairs or coaxial drops 22 depending on the service required in eachliving unit. Typically each living unit will be provided with three DS0channels, two channels for providing (POTS) and a third channel reservedfor future applications such as the D-channel for ISDN.

Referring to FIG. 2 there is shown greater detail of the LCX-50 core 24as used in the CO 10 and RT 12. The LCX-50 core 24 utilizes anon-blocking switch fabric in the form of a time slot interchanger 26which allows for switching of the various subscriber channels. In the RT12 the time slot interchanger 26 allows the subscriber channels fromONUs 16 to be loaded and groomed over the RT to CO feeder 14 for optimumcapacity and ease of administration. As shown in FIG. 2 several RT cores24 can share the same feeder 14 to provide a distributed arrangement foradditional flexibility and channel density. The ability of the RT togroom and reassign subscriber channels to different time slots allowsmore flexibility in the planning and placement of ONUs. The time slotinterchanger 26 utilized in the core is constructed as shown in U.S.patent application Ser. No. 295,887 filed Jan. 11, 1989, which isincorporated herein by reference.

The configuration shown in FIG. 2 is adapted for use with a voice-gradeanalog switch interface and is thus a UDLC system based on a LCX-50core. It is to be understood that a LCX-50 core can also support asystem for use with an IDLC configuration and that the LCX-150 corecould be used in an IDLC configuration that provides TR-303compatibility.

The system shown in FIG. 2 includes a COT in CO 10 and a RT 12 having aplurality of cores 24 connected to the COT via a SONET OC-1 feeder 14.Optical distribution links 18 extend to the ONUs 16. Interface to theanalog switch is provided by metallic line shelves 28 which accommodatechannel unit plug-ins to perform the analog/digital conversions on thetransmission signal and present voice frequency and baseband interfacesto the switching system. Up to seven line shelves 28 can be serviced byan LCX-50 core 24, with each line shelf providing 96 subscriber lines,for a total of 672 lines. When CO 10 is updated to a digital switchproviding an integrated TR 303 interface, the LCX-FTC system can easilybe upgraded to the new digital switching environment.

In the RT 12, the core 24 is connected to an Optical Distribution Shelf(ODS) 30 which provides the housing for plug-in electronics that providethe fiber optic interfaces to the ONUs. The ODS 30 is used in place ofthe metallic line shelves 28; however, if some metallic lines areterminated at the RT 12, a number of shelves may be equipped formetallic lines, as shown at 32. However, each metallic line shelfreduces the number of ONUs served by the ODS by four. A fully-equippedODS has positions for 28 optical interfaces; however, only 24 are usedfor residential applications.

The residential ONUs 16 are sealed enclosures contemplated for use in aneighborhood right-of-way near the subscriber residence that it serves.The ONU provides electronics that perform the optical/electricalconversions required and also houses channel plug-in units that providethe narrowband interface to the living units. The narrowband channelplug-in units utilized in the ONU are substantially identical to thoseused in the LCX-50 metallic line shelves.

In many instances, a living unit containing customer premises equipmentmay be connected directly to the CO 10 without the need of a digitalloop carrier system, such as the feeder link between RT 12 and CO 10. Insuch instances the equivalent of RT 12 would be co-located with the COequipment. When the RT is co-located in the CO, economical electricalSTS-1 connections may be used in place of the optical OC-1 feeder.

In FIG. 2, there is shown a Power Services Module (PSM) 34 associatedwith groups of ONUs 16. The PSM 34 is a free-standing cabinet designedto provide power to the active elements contained in the ONUs. Alarmconnections 36 are also provided between the PSM and an ONU forproviding alarm signals back to the RT or CO in the event of a failurein the PSM 34.

It should be noted that up to seven LCX-50 cores 24 may be connectedtogether in one RT site, utilizing OC-1 or STS-1 interconnections.Switched video signals may be provided to the ODS 30 in each LCX-50 core24.

FIG. 3 shows an arrangement wherein an OC-1 feeder 14 from the CO 10 isterminated at one LCX RT core 24, with additional LCX RT cores 25interconnected with electrical STS-1 high-speed links 38. With this typeof add-drop arrangement, the timeslots or channels in the OC-1 feeder 14from the CO can be efficiently utilized, even when the channel capacityof all ONUs is not fully utilized. The last LCX RT core 25 in theadd-drop string of cores may be equipped with an FTM-OC1 interface 40 tocontinue the string of cores to another RT site via another OC-1 feeder42.

The ODS 30 is responsible for providing an interface between the LCX RTcore 24 and the distribution fibers 18 to the ONUs 16. The transport andcontrol connections between the LCX RT cores 24 and 25 and the ODS 30sare via 4 Mb/s balanced serial bus links referred to as Serial BusInterfaces (SBI) 44. The SBI is an internal electrical bus used in theSONET access products of Alcatel and is fully described in theafore-mentioned U.S. patent application Ser. No. 351,458, filed May 12,1989, which is incorporated herein by reference. The SBI includes ausable payload of 24 DS0 channels or one DS1 signal. The SBI is uniquelyused to supply the distribution fibers 18 for the local loops. Theoptical signal transmitted over distribution fibers 18 is also at a 4Mb/s serial data link, and is essentially an optical extension of theSBI.

It should be noted that the OC-1 feeder line 14 is redundant andcomprises lines A and B, said redundancy is carried through the LCX-50core and also in the SBIs 44 which are also shown as A and B SBIs. Itshould be further noted that in FIG. 2, there are provided fiber optictransceivers (FTM) 43, which may be replaced by STS-1 electricaltransceivers (STT) if the feeder line is a limited distance electricalSTS-1 line, as opposed to an optical carrier. In addition, the LCX-50cores include Serial Bus Transceivers (SBT) 46 for interfacing with theSBIs 44. The LCX-50 core 24 located within the CO 10 also includes aSerial Bus Expansion unit (SBE) 48 to facilitate connection toadditional line shelves 28.

Referring to FIG. 4, there is shown greater detail of the ODS 30 usedwith the cores 24 of the RT 12. The ODS 30 is used in place of ametallic line shelf and provides for the optical connection to the ONUs16. The ODS includes, for residential purposes, 24 Optical DistributionUnits (ODU 101) 50, each connected with a fiber pigtail 52 forconnection to the distribution fibers 18. Each ODU 50 is connected tothe LCX 50 core 24 via a pair of redundant SBIs 44. The ODU 50essentially performs an electro-optical conversion of the electrical SBIsignal to an optical SBI signal. The ODU 50 is also adapted to receiveswitched video signals from broadband equipment and to FrequencyDivision Multiplex the video signals with electrical SBI signals, whichwill be described hereinafter.

Each ODS 30 is further provided with a Common Shelf Alarm Unit (CSAU)53. A Remote Measurement Unit Interface (RMUI) 54 may be provided in theODS, only one RMUI is necessary per RT. The components of the ODS 30 areinterconnected by a Low-Speed Serial Link Interface (LSSLI) 56 andreceive power via a line 58. A Balanced Serial Link Interface (BSLI) 60connects the CSAU 53 and the RMUI 54 with the LCX-50 core. A line 62connects the RMUI 54 with the remote measuring unit and functions as aTest Access Path (TAP).

Referring to FIG. 5, there are shown details of how an ONU 16 fits intothe overall system. Two optical fibers 18, one active and one spare, arereceived from RT 12. The active fiber carries narrowband and broadbandsignals, while the spare fiber is provided to carry broadband videoservice to any additional living unit over four units provided withvideo service. The narrowband and broadband signals on the active fiberare combined at the RT using Frequency-Division Multiplexing (FDM). Thenarrowband data occupies the spectrum from 0-50 MHz, while the broadbandsignal occupies the spectrum from 60-780 MHz.

The ONU 16 can serve up to eight living units, with three DS0 channelsavailable per living unit. For each living unit, two subscriber drops,typically used for POTS, are available, with the third DS0 channelreserved for future applications, such as the D-channel for ISDN. ThePOTS subscriber drops are provided at outputs 64 and are represented by16 twisted wire pairs. The third DS0 channel output is not shown in FIG.5.

The ONU also provides video coax cable drops 66 for subscriber access tohigh-quality broadband signals. It is contemplated that a business ONUwill provide more channel capacity and services per ONU than theresidential ONU shown in FIG. 5. The ONU 16 receives its power from thePSM 34 over line 35 at a nominal voltage of -130 VDC. Line 36 connectsthe power service module 34 with the ONU 16 to provide PSM alarm andstatus information. Line 36 is only used between the PSM 34 and one ONU,it is not needed for all ONUs. The ONU is also provided with an output68 as a craft port for an RS-232 connection. If desired, the -130 VDCpower could be provided from a local power source, such as residentialpower.

Referring to FIG. 6, there is shown a more detailed block diagram of anONU 16. The integrated narrowband and broadband signal is received fromthe RT 30 over a distribution fiber 18 which is connected to an OpticalDistribution Unit (ODU 201) 70. The ODU 70 converts the optical signalto an electrical signal and includes a lowpass filter which separatesout the narrowband signal from the integrated signal. The narrowbandsignal is in the form of an encoded serial bus interface (SBI) datastream, which signal is sent to a Line Shelf Access (LSA) 72 whichfunctions to distribute the signal to various time slots assigned tocards inserted in the ONU shelf. The broadband video is filtered fromthe electrical signal and then sent to a Switched Video Distribution(SVD) card 74. The SVD 74 provides video coax drops 66 to four livingunits 20 requiring video service. When more than four living units areto be serviced with video, a second distribution fiber 19 must beutilized and is connected to a Switched Video Distribution Receiver(SVDR) 76, which provides video coax drops 66 for four additional livingunits 20.

The ODU 70 has a video input for receiving upstream video from theliving units 20.

Many of the components of the ONU 16 are substantially identical to thestandard metallic line shelf components utilized in the Alcatel AccessProducts and are described in the afore-mentioned U.S. Patents andPatent Applications. The LSA 72 is described in U.S. patent applicationSer. No. 452,291, filed Dec. 15, 1989, which application also describesthe Line Shelf Processor (LSP) 73, said application being incorporatedherein by reference. In the present invention, the LSP 73 has additionalcontrol functions due to the video distribution handled by the ONU. TheLSA 72 is connected to most components of the ONU via a Line UnitInterface Bus (LUIB) 76. The LUIB is described in detail in U.S. patentapplication Ser. No. 451,436, filed Dec. 15, 1989 and is incorporatedherein by reference.

The narrowband metallic DS0 service is provided by line cards 78 whichare connected to a terminal block 80 for connection to twisted pairs 64to be provided to the living units 20. A standard Test Access Unit (TAC)82 is connected to an ONU Test Unit (OTU) 84 for test purposes. ABroadband Interface Unit (BIU) 86 is provided for controlling thedistribution of the broadband signals. A terminal block 88 is providedto receive the DC power input and the alarm information from the PSM 34.Terminal block 88 is connected to a DC/DC converter and ring generator90 which provides ring signals, alarm and control information.

An ONU Port Unit (OPU) 75 provides an RS-232C craft port forprovisioning channel units or to logon to the RT DNC. The OPU collectslocal ONU alarms and provides an alarm communication interface betweenthe PSM 34 and the CO 10.

Referring to FIG. 7, there is shown a system diagram for the provisionof broadband video service. The CO 10 receives a plurality of videochannels from a video headed 92 connected to the CO 10 via an opticallink 94. It is contemplated that typically 192 switched video channelswill be provided to remote terminal 12. Other video providers 96, suchas providers of video on demand, may be connected to the CO 10 by anoptical link 98. The program channels are transported to the RT 12 viaFM video supertrunks 100. Such FM video supertrunks are commerciallyavailable and are in common use for other video transport applications.The video channels between the video service providers and CO, orbetween COs, do not necessarily have to be transported in an FM format.These links can be the standard AM-VSB or other digital formats.However, the format must be converted to FM within the LCX-FCX frequencyplan prior to interfacing with the LCX-FTC RT-12 broadband equipment. FMis used for the video distribution format in the present invention, dueto its noise immunity compared to the AM-VSB system, and also due to theavailability of components designed for satellite distribution of videosignals. The FM system is similar to common satellite signals and istherefore compatible with most HDTV formats that have been proposed,both analog and digital.

Referring to FIG. 8, there is shown a block diagram of an RT 12illustrating the video distribution system. The broadband videotransmitted between the CO 10 and the RT 12 is transmitted on eight FMsupertrunks 100, each supertrunk transporting twenty-four 30 MHz-widechannels occupying a spectrum of 60-780 MHz. Thus, eight supertrunkswith 24 channels each provide a total of 192 video channels for thesubscribers to choose from. The eight supertrunks can be terminated atthe RT or can continue to another RT. The supertrunks 100 are connectedto the video transport equipment 102, which essentially comprises eightoptical-to-electrical converters for converting the optical signals fromthe eight fibers to electrical signals, and eight electrical-to-opticalconverters for converting the electrical signals back to optical signalsfor transmission on an additional eight fibers to a next RT. Theelectrical video signals between the converters are tapped off and areprovided to eight RF video distribution buses 104 for connection toeight Video Line Shelves (VLS) 106. Up to four VLSs 106 provide outputto the ODS 30 for ONUs that are providing video service for up to fourliving units on a primary distribution fiber 18. For situations where anONU is providing video service to more than four living units,additional VLS 106 are connected to a Switched Video Transmitter Shelf(SVTS) 108. The SVTS 108 provides a second fiber 19 to the ONU forproviding video to additional subscribers.

A Video Controller Shelf (VCS) 110 receives control signals from the LCXcore 24 for controlling Video Line Cards contained within the VLS 106.The LCX core 24 receives the control signals from the living units 20over fiber 18 via the ONU. The control signals select the video desiredby the subscriber.

FIG. 9A and 9B are a functional block diagram of the LCX-FTC broadbandRT and the ONU. The RT 12 receives the broadband video on the eight FMsupertrunks 100 at the video transport equipment 102, where the opticalsignals are converted to electrical signals and thereafter arereconverted to optical signals for transmission to the next RT or CO.

The eight electrical RF signals are provided on coax buses 104 fordistribution within the RT 12. The eight video distribution buses 104are routed to the VLSs 106. There can be 1-8 VLSs, depending upon thenumber of switched video channels required per ONU and the number ofONUs being served. Each VLS 106 can provide six video channels for eachof 24 ONUs. As the number of video channels required per ONU increases,more VLSs can be added to provide the additional capacity. Each slot inthe VLS is dedicated to a particular ONU. Thus, each VLS 106 has slotsfor 24 VLCs 112, with each VLC servicing a single ONU. If foursubscribers serviced by an ONU require six channels of video services,there will be four VLSs providing video to the particular ONU. With amaximum configuration of eight VLSs, a total of 48 video channels can beprovided to each of the 24 ONUs. Each VLS has power splitters andamplification to distribute the eight video buses to each of the 24 VLCsthat it houses. Each VLC can select six channels from the eight videobuses and functions to convert the selected video channels to adistribution channel frequency that is assigned to the particularsubscriber. In the event that it is desierable to provide less than sixchannels to each subscriber, LSP 118 can control the VCU 116 so that oneVLC 112 can provide channels to more than one subscriber, therebyreducing the number of VLCs required. This subscriber distributionchannel is one of 24 channels in the 60-780 MHz range that is sent tothe ONU over the fiber link 18. The 60-780 MHz spectrum is sub-dividedinto four sections, each with six channels for a bandwidth of 180 MHz,one section for each subscriber. For living units 1-4, up to 24 videochannels are provided to ODU 50 from VLSs 1-4 and are carried over thesame primary fiber link 18 used for the narrowband services. For livingunits 5-8, the second fiber link 19 is used to provide distribution ofan additional 24 channels per ONU. In such a case, the SVTS 108 is usedin the RT 12 to house up to 24 Switched Video Distribution Transmitter(SVDT) cards 114 for providing electrical-to-optical conversion for thecombined video signals from the VLSs 5-8 needed for serving living units5-8.

For control and ease of administration, each ONU is assigned aparticular VLC slot in each of the VLSs 106. As an example, ONU #4 isassigned to the VLC installed in slot #4 of all of the VLSs. The outputsof the VLCs in slot #4 of the VLSs 1-4 are summed together and amplifiedand then routed to the ODU 50 in slot #4 of the ODS 30, which terminatesthe primary fiber link 18 from ONU #4. Likewise, the output of the VLCsin slot #4 of the VLSs 5-8 are summed together and amplified and thenrouted to the SVDT 114 in slot #4 of the VTS 108, which terminates thesecond fiber link 19 from the ONU #4.

Program selection is made by the use of an FM set-top converter 21located at the subscriber's television set. The set-top converter may besimilar in design to pre-existing converters, but must be adapted toselect one of 192 program channels available at the RT video transportequipment 102. Up to six video channels are simultaneously available tothe subscriber, with a set-top converter required for each channel. Theset-top converter may include a variety of consumer features, includingon-screen display, volume control, digital-audio and baseband videooutput.

Channel selection requests from the set-top converters are extracted bythe SVD 74 and SVDR 76 in the ONU and are sent to the BIU 86. The BIU 86combines the channel requests and places them onto an upstreamnarrowband video control channel, DS0 #30, for transport back to the RT12. At the RT, the DS0 #30 video control channel from the ONU is sentalong with the narrowband service DS0s from the ONU over an active SBIlink 44 from the ODU 50 to the core 24. At the core, the video controlchannel DS0s from each of the 24 ODUs 50 are combined into one SBI 166and are sent to the VCS 110.

The core 24 receives broadband network management and SONET overheadsignals from an operations support unit 167. The SBI 166 is also used tosend command and control information to the VCS 110 using the VI channelof the SBI, as explained in U.S. patent application Ser. No. 547,383,filed Jul. 3, 1990, now U.S. Pat. No. 5,027,349, which is incorporatedherein by reference.

The VCS 110 is divided into quadrants, with each quadrant terminating anSBI from one RT core 24. The shelf houses up to 48 dual channel VideoControl Units (VCUs) 116, 12 per quadrant.

The VCS 110 also contains a plurality of Line Shelf Processors (LSP) 118connected to Line Shelf Access (LSA) units 120. The LSAs 120 areconnected to the VCUs 116 by a Line Unit Interface Bus (LUIB) 170. Theoperation of an LUIB is described in U.S. patent application Ser. No.451,436, filed Dec. 15, 1989, now U.S. Pat. No. 4,993,019; and thestructure of an LSA 120 and an LSP 118 are described in U.S. patentapplication Ser. No. 452,291, filed Dec. 15, 1989. Both of theafore-mentioned applications are incorporated herein by reference.

The LSA 120 directs the video control channels to the appropriate VCUsin the VLS.

Each half of a VCU 116 is provided with a video control channel forcontrolling the VLCs 112 that are in the same slot position in each VLS106. Each video control channel controls the VLCs for one slot positionin each VLS serving the same RT core.

Upstream video received from living units by the ONU 16 is provided tothe ODU 70 of the ONU and is transmitted to the ODU 50 over fiber 18.The upstream video is summed with upstream video from other ODUs 50 andis provided to the video network over a fiber 122.

The fiber optic link 18 between the RT and the ONU uses standardtelephone communication single-mode optical fiber, and a nominaltransmission wavelength of 1310 nm. The link can be up to 4 km inlength, and one fiber is the primary fiber that carries both narrowbandand broadband video signals. Both directions of transmission areprovided on the same primary fiber at the same wavelength by use ofoptical separation in the ODUs of both the RT and the ONU. A seconddistribution fiber 19 is used when video service is required to anyadditional living units over the number four. The second fiber isdeployed along with the primary fiber but remains unused until needed.The primary fiber 18 uses frequency-division multiplexing (FDM) toprovide both narrowband and broadband capability over the same fiber andthe same wavelength. The spectrum from 0-50 MHz is reserved fornarrowband data, while the video signal occupies the spectrum from60-780 MHz. The second fiber, when deployed, carries downstream videoonly. The video channels in the second link are also frequency modulatedand occupy the same frequency range as those in the primary link.

Referring to FIG. 10, there is shown in greater detail the structure ofa VLC 112, which contains six tuner circuits, each of which selects arequested video channel from one of the eight buses 104. The VLCconverts the selected video channel to a distribution channel frequencythat is assigned to a particular subscriber. This distribution channelis one of 24 channels in the 60-780 MHz range that are sent to the ONUover a fiber link 18 or 19. The 60-780 MHz spectrum is sub-divided intofour sections, each six channels wide, one section for each subscriber.

The tuner circuits of the VLCs 112 are controlled by a microcontroller124, which is connected by a serial link 126 to the VCUs 116 in the VCS110. Each tuner circuit includes an 8:1 selection switch 128 controlledby the microcontroller 124 for connecting one of the eight buses to atuner 130. Tuner 130 receives a local oscillator frequency controlled bythe microcontroller 124 and provides an intermediate frequency signal at850 MHz to a bandpass filter 132. The local oscillator frequency ischosen to be higher than the highest input frequency received from abus. Thus, the tuner 130 and the bandpass filter 132 select a particularchannel from the available inputs. The selected channel is thereafterconverted to a distribution channel frequency, assigned to a particularsubscriber, using the converter 134. Converter 134 receives a localoscillator frequency controlled by microcontroller 124 to provide anoutput signal in the original 60-780 MHz bandwidth. The distributionchannel frequency is passed through a lowpass filter 136. The sixselected channels are summed and amplified and then provided to acombiner located in a coaxial management tray 138 shown in FIG. 9. Thesix channels are combined with six channels from each of threeadditional VLSs, and the 24 channels are provided to the ODU 50.

Referring to FIG. 11, the 24 video channels from the primary fiber 18are demultiplexed via the ODU 70 and converted for subscribers 1-4 bythe SVD 74. The optical signal from the second fiber 19 is demultiplexedand converted for subscribers 5-8 by the SVDR 76. The SVD 74 and theSVDR 76 place the subscriber's 180 MHz-wide slot into the frequencyrange of 330-510 MHz before being amplified and placed on thesubscriber's coaxial drop 22. The 330-510 MHz range provides six 30-MHzwide slots for transporting six simultaneous video channels to theliving units. The set-top converter box 21 at the subscriber's premisesdemodulates the selected program signal in FM format and provides an RFmodulated AM-VSB or baseband video signal to the television set or videomonitor.

FIG. 12 illustrates the details of the SVD 74 and is somewhat similar tothe SVDR 76. The only difference between the SVD 74 and the SVDR 76 isthat SVDR 76 receives an optical signal which is converted with anoptical-electro converter to an electrical signal, after which the twocircuits are identical. The electrical signals from the ODU 70 in thecase of the SVD 74 are provided to a plurality of bandpass filters 140which pass selected frequency ranges applicable to the associated livingunit, the passed signals are mixed with signals from local oscillators142 to translate the signals to a frequency band that can be accepted atthe living units. The signals in the uppermost and lowermost sub-bandsare passed through additional bandpass filters 144 prior to beingamplified in amplifiers 146. After being amplified, the signals passthrough capacitors 147, which are used to block DC votage induced oncoaxial drops 122 to the subscribers. The middle two sub-bands arepassed through additional bandpass filters 148, after which the signalsare mixed with additional local oscillator signals from localoscillators 150, with the mixed signals being passed through additionalbandpass filters 152, after which they are amplified by amplifiers 154and passed to coaxial drops 22 through capacitors 147.

RF chokes 153 are attached to the outputs of amplifiers 146 for thepurpose of extracting low frequency carrier or baseband data used tocontrol and communicate with the customer premises equipment, which matbe a set-top converter.

Referring to FIG. 13, there is shown the BIU 86, which receives channelselection requests from the SVD 74 and the SVDR 76 which extract therequests from the signals received over the coax drops 22 from thesubscriber's set-top converters 21. A carrier frequency is used forcommunication to and from the set-top converters 21. A datacommunication network will thus be formed between the BIU 86 and all ofthe set-top converters 21 served from a given ONU. Frequency shift keyed(FSK) carriers are preferred. The frequency is between 5-50 MHz to passthrough DC-blocked components and to prevent interference with otherservices, such as if the coax is used for broadcast CATV servicesbetween 50-330 MHz. A standard communications protocol for this networkis used. On the SVD and SVDR the FSK carrier(s) would be extracted by afilter network (shown as an inductor and capacitor for simplicity).Collision management circuitry is required to handle contention betweenmultiple set-top units.

The RF connection 160 between the SVDR and SVD is allocated as aprovision in the event that all 24 channels of video service for fourliving units cannot be transmitted economically on the primary fiber inthe first generation first generation of equipment. Additional channelscould be transmitted to the ONU using a second fiber and theoptical-to-electrical converter on an SVDR without much of the othercircuitry. The recovered signal could be connected to the SVD via the RFconnection to augment the channels.

The details of the BIU 86 are shown in FIG. 14. The BIU 86 includes apair of FSK transceivers 156, collision management circuits 158, eachconnected to a microcontroller 160. The microcontroller 160 is connectedto SVD 74 and SVDR 76 via a bus 161 for receiving and transmitting data,tests, alarms and control information. The microcontroller 160 isconnected to a line unit interface circuit 162, which is connected to aLUIB 164 for connection to LSA 72. The structure and operation of theline unit interface circuit 162 is similar to that described in U.S.patent application Ser. No. 451,436, filed Dec. 15, 1989, now U.S. Pat.No. 4,993,019, which is incorporated herein by reference. The BIU 86combines the channel requests from each subscriber and places them inthe upstream narrowband video control channel DS0 #30 for transport backto the RT 12 over link 18.

The microcontroller 160 and the transceiver circuitry translate thecommands into a digital data packet for transmission to the remoteterminal in a control channel (DS0) on the SBI. Note that this path isbidirectional. Channel change commands are described as the typicalexample. Information may also be sent to the subscriber. For example, ifa channel change request is denied, that information would betransmitted to the subscriber. Other dialog with the subscribers andset-top converters (diagnostic test) will also be possible. In addition,alarms on the broadband cards (BIU, SVD and SVDR) in the ONU could becommunicated over the broadband control channel.

At the RT 12, the DS0 #30 video control channel from the ONU is sentalong with the narrowband service DS0s over the active SBI link 44. Atthe RT core 24, the video control channel DS0s from each of the 24 ODUs50 are combined into one SBI 166 and are sent to the VCS 110. The fourcores 24 and 25 shown in FIG. 3 each have an SBI 166 connected to theVCS 110, as shown in FIGS. 15A and 15B. In one quadrant of the VCS 110,the 12 VCUs 116 handle the control DS0s for 24 ONUs. The serial link 126connects the VCUs 116 to the VLCs 112 contained in the VLS 106. The VLCsin similar slots of the VLSs are connected together for control by avideo control channel from a single ONU, as is illustrated in FIG. 15Aand 15B.

FIG. 16 shows the circuitry of a VCU 116, which includes a line unitinterface circuit 168 connected to the LUIB 170. The line unit interfacecircuit 168 divides out to DS0 channels for controlling the VLCs. TheDS0 channels are connected to a microprocessor 172, which is furtherconnected to RAM 174. Microprocessor 172 provides two outputs which arebalanced serial links 176, which function to provide signals to theserial link 126 providing the control to the VLCs 112.

The VCUs 116 at the RT 12 convert two DS0 channels into two outputs perVCU. However, the VCU outputs are bidirectional serial buses. The VCUcontains information such as channel authorization and billing data. Forexample, once a channel change request is received by the VCU, the unitwould decide if that subscriber is authorized to tune to that particularchannel. The command would then be sent along the serial link 126 to berecognized by the microprocessor in an available VLC 112 in the slotcorresponding to the ONU 16 in a VLS 106. The VLC microprocessor wouldthen command the switch, tuner and converter for an available VLCchannel to select the desired channel and place in the appropriatesub-band for the subscribers.

Thus, the present invention provides a truly integrated fiber optictelecommunications network providing switched video and standardnarrowband telephone services on a single optical fiber which extends tothe curb adjacent the subscriber premises. Through the use of switchedvideo, the subscriber has access to 192 video channels, with up to sixchannels being available simultaneously to each subscriber. Subscriberchannel selection is transmitted upstream to the video switching pointusing a narrowband DS0 channel for transmitting the selections of agroup of subscribers. This transmission is transparent to the subscriberand does not affect the POTS service provided to the subscriber.

The system allows video providers to offer a variety of different typesof video service. Upstream video may also be transmitted from each ONU.The use of frequency modulation provides improved performance, and theadditional use of frequency division multiplexing of the broadband andnarrowband signals over the same fiber greatly reduces the cost and sizeof the equipment. The integration of the present system allows thebroadband section to utilize the reporting alarms, status monitoring andtesting, as well as remote provisioning and inventorying that arepresently available in narrowband SONET systems.

What is claimed is:
 1. An optical distribution shelf for a remoteterminal, comprising:a plurality of optical distribution units eachincluding means for receiving an electrical TDM baseband signalcomprising a plurality of telephony channels, means for frequencydivision multiplexing a frequency modulated video carrier electricalsignal with said baseband signal, and means for providing an opticaloutput corresponding to said frequency division multiplexed electricalsignals; and means for interfacing said optical distribution units witha microprocessor controller in a cross-connect core controlling thesource of the baseband signals wherein said cross-connect core isconnected to an optical carrier level N(OC-N) optical signal.
 2. Anoptical distribution shelf as described in claim 1, wherein theinterface means comprises:a common shelf alarm unit connected to each ofsaid optical distribution units and to said microprocessor forcollecting alarm and inventory information; and a remote measurementunit interface connected to said common shelf alarm unit, themicroprocessor and to a remote measurement unit for providing a testaccess path (TAP) for line testing.